The present invention relates generally to metallurgical apparatus and more particularly to apparatus for tapping a wall of a metallurgical vessel.
In order to open the tap hole of a shaft furnace such as a blast furnace, a drilling machine is utilized which is suspended from an apparatus that selectively displaces or moves the drilling machine into an operative position for drilling the tap hole and into an inoperative position upon completion of the drilling operation. Examples of such apparatus are illustrated in U.S. Pat. No. 3,121,769 issued on Feb. 18, 1964 to Walter Horn.
An important object of such tap hole drilling apparatus is to properly align the drilling machine in its operative position each time the furnace is tapped, such that it drills the same tap hole passage with the same inclination every time. Between each melt, the tap hole is filled with refractory clay and at the end of each melt, it is important that the same tap hole passage be drilled on each repeated opening. Otherwise, intersecting bore holes of different inclinations will result, such that on subsequent tap hole drilling operations, the drills are deflected and become jammed, and gradually the strength of the tap hole is reduced leading to possible premature ruptures. This will also cause the tap hole to eventually erode away into an undesirably much larger diameter.
The prior art tap hole drilling apparatus which utilize a swinging boom to position the drilling machine requires considerable room to operate, in order to position the drilling machine in the operative position and then in the inoperative position. This required the use of excessive working space for the machine which could otherwise be better put to use in the plant, and further limits the size of the drilling machine, requiring the use of smaller drilling machines than would otherwise be desired. In view of the fact that smaller drilling machines than desired must be utilized with the tap hole drilling apparatus of the prior art, the drilling time of the tap hole is undesirably increased.
In addition, the prior art drilling apparatus for the most part station the drilling machines in a suspended free-standing position such that the drilling machine is not positively positioned in relation to the tap hole to insure drilling of the same tap hole passage each time. Those prior art drilling machines which do employ some type of positioning mechanism, use a mechanical latching system to latch the drilling machine directly to the vessel to be tapped in order to positively position the machine. This is very undesirable, as the drilling machine cannot be rapidly displaced from the drilling operation without first unlatching it from the vessel. This time required in unlatching the drilling machine from the vesssel can be extremely critical, as damage will quickly occur to the drilling machine once the pour has started. In addition, the possible failure of the mechanical latching mechanism makes the situation even more critical, as a failure of the latching mechanism could cause irreparable damage to the drilling machine if the pour from the tap has already started and one is unable to detach the drilling machine from the furnace.
Another problem encountered with the tap hole drilling apparatus of the prior art is that it is desirable to position the drilling machine in its operative position for tap hole drilling at a relatively slow rate, and yet be able to retract the drilling machine very rapidly once the tap hole has been drilled. The prior art apparatus does not make provision for this, and the result is that the drilling machine is unduly subjected to excessive heat conditions at the time the furnace is tapped.
It is a principal object of the present invention to provide a tap hole drilling apparatus which is devoid of the afore-described disadvantages and which can positively align and position the drilling machine without the risk of mechanically latching it to the furnace, takes a minimum amount of space for positioning from the operative position to the inoperative position, while permitting the use of a relatively large and fast operating drill, and permits retraction of the drilling machine from the drilling operation at very rapid rates, yet permits positioning of the drilling machine in the operative position for tap hole drilling at slower rates.